The PT100 temperature sensor can be wired in a two-, three-, or four-wire system.
The two-wire system is to connect a wire at each end of the RTD temperature sensing element, the wiring is simple, the installation cost is low, but there is an additional error of lead resistance, it is not suitable for high-precision temperature measurement occasions, and the lead wire and wire should not be too long.
The three-wire system is to connect two leads at one end and one lead at the other end of the RTD element. This connection method can eliminate the influence of wire resistance on the measurement, so it is most widely used in industrial inspection. Especially in the case of narrow temperature measurement range or long wire, and the temperature of the wire is easy to change, the three-wire system must be considered.
The four-wire system is mainly used for high-precision measurements by connecting two leads at each end of the temperature sensing element. In PLC applications, two wires are sent out at each end, two are connected to the PLC output constant current source, and the PLC measures the voltage on the PT100 through the other two to cancel out the wire resistance. The four-wire system has the highest accuracy, but it is also relatively expensive.
The specific wiring method to use needs to be comprehensively considered according to the accuracy requirements and cost. In practical applications, the three-wire wiring method is generally adopted, because this method can not only eliminate the influence of wire resistance, but also has high accuracy and low cost.
In addition, it should be noted that if the PT100 temperature sensor needs to be connected with a long wire, then the size and length of the wire should be as same as possible to reduce the error. At the same time, in order to ensure the accuracy of the measurement, the performance of the sensor and the connection of the wires should be checked regularly, and necessary maintenance and adjustments should be carried out.